The main suspects in the Boston Marathon bombing are two brothers from Chechnya, a Russian republic that has been the scene of cyclical revolts and brutal crackdowns for the past 200 years.

How did it become part of Russia?

The Caucasus region was conquered by Czarist Russia, whose armies took three decades to overcome the resistance of the guerrilla warriors. The long war, whose brutal and treacherous nature was brilliantly captured by Russian writer Leo Tolstoy in his last novel, Hadji Murat, was finally won by Russian Gen. Mikhail Yermolov, who used scorched earth tactics, hostage taking, and deliberate bloody civilian massacres to crush the Chechen rebels.

Chechnya has erupted in revolt every time the Russian grip has weakened ever since, notably amid the chaos following the Bolshevik Revolution in 1917 and after Nazi Germany invaded the USSR in 1941. Soviet dictator Joseph Stalin was so infuriated by Chechen disloyalty in World War II that he ordered the entire Chechen nation – half a million people – deported to Central Asia in 1944. An estimated 150,000 Chechens died on the bitter winter march.

The Chechens were allowed to return home after Mr. Stalin died, but they declared independence as the USSR crumbled in 1991. The Russian Army invaded in 1994, but withdrew in defeat after two years of futile war and an estimated 80,000 mostly civilian casualties.